Cytokines, such as interleukin-1 (IL-1) and tumor necrosis factor (TNF), are molecules produced by a variety of cells, such as monocytes and macrophages, which are mediators of inflammatory processes. Interleukin-1 is a cytokine with a wide range of biological and physiological effects, including fever, prostaglandin synthesis (m, e.g., fibroblasts, muscle cells and endothelial cells), T-lymphocyte activation, and interleukin-2 production.
The Interleukin-1 superfamily: The original members of the IL-1 superfamily are IL-1α, IL-1β, and the IL-1 Receptor antagonist (IL-1RA). IL-1α and -β are pro-inflammatory cytokines involved in immune defense against infection. The IL-1Rα is a molecule that competes for receptor binding with IL-1α and IL-1β, blocking their role in immune activation. Recent years have seen the addition of other molecules to the IL-1 superfamily including IL-18 (see Dinarello (1994) FASEB J. 8(15):1314-3225; Huising et al. (2004) Dev. Comp. Immunol. 28(5):395-413) and six more genes with structural homology to IL-1α, IL-1β or IL-1RA. These latter six members are named IL1F5, IL1F6, IL1F7, IL1F8, IL1F9, and IL1F10. In accordance, IL-1α, IL-1β, and IL-1RA have been renamed IL-1F1, IL-1F2, and IL-1F3, respectively (see Sims et al. (2001) Trends Immunol. 22(10):536-537; Dunn et al. (2001) Trends Immunol. 22(10):533-536). A further putative member of the IL-1 family has been described called IL-33 or IL-1F11, although this name is not officially accepted in the HGNC gene family nomenclature database.
Both IL-1α and IL-1β are produced by macrophages, monocytes and dendritic cells. They form an important part of the inflammatory response of the body against infection. These cytokines increase the expression of adhesion factors on endothelial cells to enable transmigration of leukocytes, the cells that fight pathogens, to sites of infection and re-set the hypothalamus thermoregulatory center, leading to an increased body temperature which expresses itself as fever. IL-1 is therefore calledan endogenous pyrogen. The increased body temperature helps the body's immune system to fight infection. IL-1 is also important in the regulation of hematopoiesis. IL-1α is a pleiotropic cytokine involved in various immune responses, inflammatory processes, and hematopoiesis. IL-1α is produced by activated macrophages, stimulates thymocyte proliferation by inducing IL-2 release, B-cell maturation and proliferation, and fibroblast growth factor activity. IL-1α proteins are involved in the inflammatory response, being identified as endogenous pyrogens, and are reported to stimulate the release of prostaglandin and collagenase from synovial cells. It is produced as a proprotein that is proteolytically processed by calpain and released in a mechanism that is still not well studied. This gene and eight other interleukin 1 family genes form a cytokine gene cluster on chromosome 2. IL-1α and its disease-causing effects are described in detail in Ibelgaufts, Lexikon Zytokine (Cytokine Dictionary), Medikon Verlag, Munich 1992, and in the literature cited therein. Reference is also made to the undesirable effects of IL-1α in, for example, Oppenheim et al. (1986) Immunol. Today 7:45-56, Durum et al. (1985) Ann. Rev. Immunol. 3:263-287 and Synnons et al. (1989) Lymphokine Res. 8:365-372. IL-1α was originally termed “catabolin” because of its effect in increasing cartilage resorption, but also as “monocyte cell factor” (MCF) because of its stimulatory effect on collagenase and prostaglandin in synovial cells, and as “leucocyte endogenous factor” (LEM) having a stimulatory effect on acute phase reactions. In addition, IL-1α has a broad spectrum of biological activities, since IL-1α is synthesized by many different cells, such as monocytes, macrophages, fibroblasts, endothelial cells and lymphocytes, and many cells possess specific receptors for IL-1α. IL-1α therefore occupies a central position as the trigger for various disorders and symptoms of disorders. These disorders are often predominantly serious disorders for which there is little or no treatment. It has been suggested that the polymorphism of these genes is associated with rheumatoid arthritis and Alzheimer's disease. IL-1 in general has been implicated in many human diseases, including arthritis, pulmonary fibrosis, diseases of the central nervous system, diabetes mellitus, and certain cardiovascular diseases.
IL-1β production in peripheral tissue has also been associated with hyperalgesia (increased sensitivity to pain) associated with fever (Morgan et al. (2004) Brain Res. 1022(1-2):96-100). For the most part, these two forms of IL-1 bind to the same cellular receptor. This receptor is composed of two related, but non-identical, subunits that transmit intracellular signals via a pathway that is mostly shared with certain other receptors. These include the Toll family of innate immune receptors and the receptor for IL-18. IL-1α and IL-1β also possess similar biological properties, including induction of fever, slow wave sleep, and neutrophilia, T- and B-lymphocyte activation, fibroblast proliferation, cytotoxicity for certain cells, induction of collagenases, synthesis of hepatic acute phase proteins, and increased production of colony stimulating factors and collagen.
cDNAs encoding the two distinct forms of IL-1 have been isolated and expressed; these cDNAs represent two different gene products, termed IL-1β (Auron et al. (1984) Proc. Natl. Acad. Sci. USA 81:7909) and IL-1α (Lomedico et al. (1984) Nature 312:458). IL-1β is the predominant form produced by human monocytes both at the mRNA and protein levels. The two forms of human IL-1 share only 26% amino acid homology. Despite their distinct polypeptide sequences, the two forms of IL-1 have structural similarities (Auron et al. (1985) J. Mol. Cell. Immunol. 2:169), in that the amino acid homology is confined to discrete regions of the IL-1 molecule.
IL-1α and IL-1β are produced as precursor peptides. In other words they are made as a long protein that is then processed to release a shorter, active molecule, which is called the mature protein. Mature IL-1β, for example, is released from Pro-IL-1β following cleavage by a certain member of the caspase family of proteins, called caspase-1 or the interleukin-1 converting enzyme (ICE). The 3-dimensional structure of the mature forms of each member of the human IL-1 superfamily is composed of 12-14 β-strands producing a barrel-shaped protein.
There is a need in the art for improved antibodies that bind IL-1β for use in new therapies against IL-1β associated diseases and for use in detecting IL-1β in samples and tissues.